UB55 univariate analysis: hi-lo contrast, group-level

1 intro

Purpose:

1. Validate runwise ub55 GLMs in terms of marginal HRFs (averaged across conditions) and high-vs-low contrast.
2. Define target TRs for each task.
3. Calculate HiLo conjunction effect, and create list of conjunction parcels.

Notes on analyses:

GLMs:

• DMCC55B
• run-wise, 1trpk, shifted TENTs
• Cuedts: terms for \(\text{trial-type (congr, incon)}\times\text{sequence (switch, repeat)}\) instead of \(\text{incentive}\)

Target TRs:

• Axcpt: 7, 8, 9
• Cuedts: 9, 10
• Stern: 11, 12
• Stroop: 2, 3, 4
• Axcpt, Cuedts, and Stern begins at roughly ~4 TRs post-cue onset, and ending at ~8 TRs post-cue onset
• Stroop begins at 2 TRs post-target onset, ends at 6 TRs post-target onset

Contrasts (on regional means):

• Axcpt: \(\text{BY} - \text{BX}\)
• Cuedts: \((\text{InConSwitch} + \text{InConRepeat} - \text{ConSwitch} - \text{ConRepeat})/2\)
• Stern: \(\text{LL5RN} - \text{LL5NN}\)
• Stroop: \((\text{PC50InCon} + \text{biasInCon} - \text{PC50Con} - \text{biasCon})/2\)

Plotting and statistical details:

• within ‘curves’ sections, ribbons indicate 95% CI of bootstrapped mean beta across subjects (one ribbon per run).
• all p-value corrections were performed whole-cortex, with FDR.
• for “stats and maps” sections, HLM was used to estimate t-statistics on the hi-lo contrast per ROI:
  • random-intercept models
  • level-I: (TR within target window)*(run)
  • level-2: subject
  • \(\beta_{trs} = b_0 + d_s + \epsilon_{trs}\)
    • \(\beta_{trs}\) is high-low contrast beta estimate
    • \(t, r, s\) are indices for TR, run, and subject
    • \(d\) is is subject-specific intercept
    • \(\epsilon\) is error

2 Network-level

Estimates are first averaged across parcels within network per subject. Group-level stats and plots are then displayed at the network-level.

2.1 marginal beta estimates (averaged across all trialtypes)

2.2 conditional (per trialtype)

2.3 contrasts

2.3.1 beta estimates

2.3.2 t-statistics

3 Parcel-level

3.1 counts of significant effects per TR

Using t-test of subject parcel means, averaged across run. Negative counts show deactivations.

3.2 contrasts

3.2.1 DMCC 34

3.2.2 Cross-task conjunction (“DMCC55B parcels”)

Here conjunction analysis is performed by feeding TR-level contrast estimates to an HLM (see description at beginning of doc).

Number of parcels identified, and parcel names:

task	n.activated
Axcpt	123
Cuedts	108
Stern	34
Stroop	176

3.2.3 Curves of “DMCC55B parcels”

3.3 Brains (contrasts)

NB: colors are reversed (black = high, yellow = low) so large positive effects can be seen on white underlay.

3.3.1 Axcpt

### Cuedts ### Stern ### Stroop